be aware that the internal crosstalk, even on a Rev.24 LPF board is quite high and, depending on the drive level, will not improve Your IM3 much. At least on the higher bands! In my case, i had seen even a deterioration of IM3 on 15 Meters and up when i was running PS from an external sampling source. But it works ok on 40 and down, usually.

Is that an indictment of the 100B in particular, or of Rev. 24 boards, which are used in all late model, 100W ANAN series radios? I'm only asking because when I was using a 200D with a Rev. 24 board in it for a few months it provided -50dBc or greater IMD suppression for me on 10M and down.

where did You see the -50dBc? On the same 200D You were transmitting with? Do not take that for granted because You see a mixed spectrum from the ext. sampler and the internal crosstalk! And PS tries to correct that mix which can appear quite good on your own screen but not so good on another sdr or spectrum analyzer which monitors the 'real' output signal. Although I'm not sure i cannot see a reason why there should be a huge difference in the level of crosstalk between the Anan models that have the same PA-LPF-Board? Do You?

I hope i could make myself clear.

But all that is obvious when You see the amount of crosstalk on my unmodified Rev.24 Anan 100:

I know Warren mentioned the max crosstalk level our radios mustn't exceed in one of his posts unfortunately i'm not able to find that now! What i know is around -20dBm is certainly to much. And it gets worse on a higher frequency. BTW i sent this screenshots to the official support and they confirmed my observation of the amount of internal crosstalk.

Don't You recall our discussion about this topic on Bills(KC9XG) Yahoo Group, Scott? Some time ago, i agree!

If your ANAN 100 is set to produce 92W of output => approximately +50dBm...and the internal feedback signal level (dup on, and no external feedback) is -10dBm...then the internal "crosstalk" coupling from the RF output to the RX1 input is (-10dBm) - (50dBm) = -60dB.

I have previously shown that, for the reason you stated in your post, when using an external amplifier whose non-linearity dominates the IMD:

The amount of improvement that can be obtained (Pure Signal on v. Pure Signal off) in IMD , in dB, in the external amplifier's output signal, is equal to the difference between the level of the feedback being provided from the coupler at the output of the external amplifier (in dBm) and the level of the internal feedback (in dBm).

For example, if the internal feedback signal level is -10dBm, and the external amplifier's feedback signal level is 5dBm... then the maximum improvement in the amplifier's output IMD is 5dBm - (-10dBm) = 15dB. If the IMD produced at the output of the external amplifier without Pure Signal active is -30dBc, then the IMD produced at the output of the external amplifier with Pure Signal active will be no better than (-30dBc) - (15dB) = -45dBc. As you pointed out, this is true regardless of the IMD improvement that the panadapter displays when the 2-tone test is turned on, and Pure Signal is activated. Note that the internal crosstalk signal level should be measured with the ANAN's output power set to the level needed to drive the external amplifier to its full power output.

Note that on 40m, and with 100W of peak output, the KXPA100 has 3rd order IMD products that are only 20dB below the principal tones in a 2-tone test... so the theoretical maximum IMD improvement of 35dB is quite useful. The panadapter shows the IMD 3rd order products dropping to below 50dB below the principal tones... with Pure Signal active... but I have not measured the IMD with a separate receiver to verify that improvement.

In the case where there is no external amplifier, the obtainable improvement in IMD at the output of the ANAN, would depend on how much of the internal "crosstalk" (in dBm) is from coupling to RX1 from the output of the ANAN's internal 100W power amplifier compared to how much of the internal "crosstalk" (in dBm) is from coupling to RX1 from sources other than the output of the ANAN's internal 100W power amplifier.

I have to say I did not evaluate the 200D I had barefoot, but only with an external 500W amplifier. Running +10dBm feedback level at the Bypass connector, even if crosstalk was -20dBm internally, that would provide some 30dB of improvement as Stu describes. The combination of the IMD from the radio itself (by far the largest contributor) and the amp was in the -25dBc range. Hence it is not surprising that I obtained better than -50dBc on all bands (except 6M, which I do not use).

thank You for the comprehensive explanation. Unfortunately i had my Anan-100 modified so I'm not able to perform the test again., and, i agree, i haven't documented all that. And I'm not in possession of a device which could show my tx signal anymore.

Stu, are these equations entirely applicable into 'real world' use? I mean can these numbers be confirmed when You hook up a spectrum analyzer or. another sdr to the output of the amp? I'm asking because i did see that increase of the IMD on the higher bands once PS was activated. And i was convinced that this was caused by the huge internal crosstalk. Would be nice if someone could provide test results of a similar setup.

I know it is possible to run PS on an of the shelf Anan-10 on external sampling with good results. A friend of mine does the same! He only needs roughly 2 Watts from his Anan-10 to drive the following amp stages. I need about 40 Watts to drive my single 3-500 to legal power which is 750 Watts in Germany.

out of curiosity, are You able to compare the spectrum Your Anan shows to an external device while performing a two-tone test? Is there any difference at all? Especially on the higher bands!

I'm asking because of this posting from Warren:

Remember, PS corrects whatever it sees.If it sees a distorted signal at the ADC input, it will DISTORT theoutput to try to correct the distorted signal. In such a situation, ifPS has "corrected", you might see a nice result on your internalpanadapter because you are looking at the same signal PS is --- thesignal coming in through the receiver ADC. However, the real TX signalmight be a totally different picture.

I can and have done that. I have a cheap USB SDR stick that I use. It's sensitivity is way down in HF but it is sufficient to see the signal from my nearby antenna at 500W. I never took a critical look at the output of the 200D I was borrowing, but my 100D with external feedback switch (it has the old revision PA/RF board), combined with my KPA500 amplifier, always looks fine, i.e. in excess of -50dBc.

It may be worth noting that I had to get the cheap SDR dongle because the older rev. 15 and 16 boards ground the input to RX2 on transmit. I had hoped to be able to use RX2 on a separate antenna to monitor what actually comes out of my main antenna on transmit, but no such luck. The newer rev. 24 boards can do this, of course, because they do not ground the RX2 input on transmit.

I haven't checked my theoretical results with a separate receiver... but perhaps some others, in addition to Scott... who have access to a physically separate SDR... can comment. Someday I will upgrade to a new SDR model, and I will use the new SDR to verify the IMD improvement produced by Pure Signal at my ANAN-10e's output (before I find a new home for the ANAN-10e).

I have a comment about using RX2 as a "separate" receiver for this purpose. I think one has to determine whether the internal crosstalk into RX2 is sufficiently low (compared to the internal crosstalk into RX1) to use RX2 for this purpose.

I have not given a lot of thought as to why turning on Pure Signal could make the IMD at the output of the final RF amplifier worse.

A (pathological?) example of how this could occur would be as follows:

1. Most of the input to RX1 is crosstalk from amplifiers in the RF chain that are ahead of the final output amplifier.

2. The distortion (IMD) produced by those earlier amplifiers in the RF chain is partially cancelled by the additional distortion being produced in the final RF amplifier (and vice-versa).

3. If Pure Signal is activated, it linearizes the chain of amplifiers that are ahead of the final output amplifier... thus removing the distortion they were producing that was partially cancelling the distortion being introduced in the final output amplifier.

All of the above could occur if one were using an external power amplifier, but none (or too little) of the output of that external amplifier was being coupled (as feedback) to RX1

w-u-2-o wrote:I can and have done that. I have a cheap USB SDR stick that I use. It's sensitivity is way down in HF but it is sufficient to see the signal from my nearby antenna at 500W. I never took a critical look at the output of the 200D I was borrowing, but my 100D with external feedback switch (it has the old revision PA/RF board), combined with my KPA500 amplifier, always looks fine, i.e. in excess of -50dBc.

This is what i can achieve here as well, Scott! After the modification and with the feedback relay!

I met a Swiss fellow who is using an unmodified 200D with external sampling. I'll try to talk to him again in order to learn what his observations are!

w-u-2-o wrote:It may be worth noting that I had to get the cheap SDR dongle because the older rev. 15 and 16 boards ground the input to RX2 on transmit. I had hoped to be able to use RX2 on a separate antenna to monitor what actually comes out of my main antenna on transmit, but no such luck. The newer rev. 24 boards can do this, of course, because they do not ground the RX2 input on transmit.

In case the Anan is modified, i wouldn't expect any difference in the amount of crosstalk between the Rev.15/16 boards and the newer ones because stray rf is mainly been picked up on the sdr board itself(roughly -60dBm as i recall). Is the rx2 bnc directly connected to the sdr boards on the rev.24 Anan's? I mean without additional relays, wires, switches and so forth? That might result in a similar crosstalk level then on a mod. rx1 path? So, it might not be worth to mess around with rx2 when You basically see the same like on rx1. Unless You want to monitor something else.

I have transplanted my 200 D in a home made enclosure and I have a coax relay which cuts off or not (switchable) the RF input to RX1 during transmit. When NO external sample is fed into RX1 during transmit there will be no Pure Signal triggering by the crosstalk RF even at 125 W output power. So crosstalk has been eliminated in my setup (improved shielding, and coax relay switching for RX1 input did it)I am still testing on samplers on my bench in order to develop a sampler small enough to be built into my Expert 1K-FA linear. So I have not investigated so far how external sampling works in detail.Concerning internal crosstalk sampling I noted big defferences from band to band. On my setup (to be seen on my QRZ.com page) crosstalk is even insufficent to trigger PS correction on 80 meters with full power ! I did notice also big differences on IMD improvements from band to band (seen on a separate Perseus receiver)- close to -50dBc from 40 to 6 m and -32dBc (very unstable jittering from -25 to -35) on 15 meters. No PS action on 80 and 160 m.

So I think internal crosstalk seems to be essentially variable and unstable and is only a lesser evil to make PS work. It is better to use an external sample from a good and linear sampler; the external feedback level may be reduced once you eliminated internal crosstalk in order not to damage your frontend.

Ban crosstalk !

73s Phil FM5GB

Last edited by FM5GB on Fri May 12, 2017 9:54 pm, edited 1 time in total.

As Phil's and other's efforts point out, there is insignificant crosstalk on the SDR board itself. It becomes a problem because of the design of the PA/RF board. Eliminate/bypass that board and crosstalk levels drop dramatically.

This all could probably have been solved with an appropriate sheet metal overlay for the PA/RF board. However since people generally only use full duplex, co-channel operations for PureSignal, it's easier to simply create a bypass path with an appropriately shielded relay and cables for that purpose. On the older revision boards the improvement is obvious. On the Rev. 24 there is improvement, but it is not as dramatic.

How much IMD suppression do we really need, anyhow? I submit that anything in excess of -50dBc is rarely needed. At -50dBc and real-world noise floors, you will notice IMD only on the largest signals, those in excess of S9+30.

i can only marvel whenever i bring up Your QRZ.com page, Phil. Oh boy, so much work! I'm convinced Your solution is the best possible! But around -60dBm crosstalk means plenty of isolation, i think! And i do not see much variation of that number over the bands here as well. And these -60dBm may result mainly from coupling directly into the sdr board which is, of course, insignificant.

I am really only interested in 6m. I have an ANAN-100D. The internal cross-talk is so high that I can only use output powers of under 32W. Also when I engage DUP to look at my TX signal it is of limited use because of front end saturation, I can only monitor at

So this means 2 things I presume:

I have a Rev 24 PA

To use DUP for either output signal quality monitoring or with an external coupler and an amp I have got to dramatically reduce the internal cross-talk.

How is this best achieved with the Rev 24 PA? I can see dramatic improvements IMD performance on 6m at 32W or less. Down to a little below -50dBc 3rd order. I am perfectly happy with this however I would like to be able to correct the whole chain.

Internal cross talk should not affect your ability to produce 100W of power on 6M. It will affect your ability to achieve a good PureSignal solution.

None of what you have noted would suffice to identify what revision PA/RF board you have. Look at this topic to determine how to do this.

Poor crosstalk performance implies that you have a revision older than 24.

To solve this problem on the old Rev. 15 and 16 boards most people have modified their radios to use an external switch to bypass the source of the problem, which is the PA/RF board. W1AEX has an excellent example of how to do this on his website here. I did the same thing on my old 100D, but I used a somewhat better switch from Dow-Key. There are many similar Dow-Key switches often available on eBay.

Finally, it is best to adjust your feedback level to approach, but not exceed, +13dBm at the RX1 input. +10dBm is generally a good number to shoot for. Although this requires more step attenuator to be used, it also maximizes the feedback-to-crosstalk ratio.

out of curiosity, are You able to compare the spectrum Your Anan shows to an external device while performing a two-tone test? Is there any difference at all? Especially on the higher bands!

Bernhard,

I've been following the thread but did not have a chance to put my ANAN-200D REV 24 to the separate receiver test until this morning. I was surprised by your report of high levels of crosstalk with your REV24 board. My original ANAN-100 REV15/16 transceiver behaved very much like your description near the top of the thread. The crosstalk was horrible above 40 meters until I did the cable re-routing modification that was worked out and documented by Bill Diaz KC9XG.

When I sold my ANAN-100 and picked up a second-hand (one month old) ANAN-200D REV 24 last April I was pleased to see that it corrected beautifully right up through 6 meters with my XTRONIC exterrnal coupler. I took the screenshots below this morning on 10 meters with the ANAN running 35 watts (the driving power needed for my amplifier) showing PS off and PS on. The difference with correction is quite significant. I get excellent correction with <5 watts right up to 100 watts. It looks very similar with the amp engaged and running at a KW or more.

I'm wondering why you were not getting similar results with your REV 24 and had to resort to the old REV 15/16 type of modification. Are you certain that your ANAN-100 is a REV 24?

73,

Rob W1AEX

The screenshots were made with my SDRplay RSP1 using SDRuno running on the same computer as the ANAN:

Pure Signal OFF - IMD not great but pretty typical of most rigs on the 10 meter band

Pure Signal ON - IMD looking quite good and light years better than anything else out there in my opinion.

ANAN 200D test setup with separate receiver

Last edited by W1AEX on Sun Mar 25, 2018 4:04 pm, edited 1 time in total.

"One thing I am certain of is that there is too much certainty in the world."

I just looked more closely at your screenshots of PowerSDR mRX PS near the top of the thread and noticed that the SATT level was zero with the Bypass on TX enabled and also when disabled. That doesn't sound right to me but then again that was version 3.2.2.7 of PowerSDR mRX PS and I don't think auto-attenuate was implemented back in the middle of 2015. I wonder how it would look with the current 3.4.9 version using Pure Signal 2.0. Are you absolutely certain that your ANAN-100 is a REV24? If it's not, that would certainly explain why you were not receiving a feedback sample with the Bypass on TX box checked. As I recall, the REV 24 rigs began to show up after February 2015 so perhaps that's a REV 15/16 board.

I'm just trying to figure out why you were having issues with crosstalk as that problem was cleaned up nicely with the REV 24 PA. When you modified the ANAN-100 did you use the procedure worked out by Bill Diaz using an external relay to open the path to the Hermes RX input?

73,

Rob W1AEX

"One thing I am certain of is that there is too much certainty in the world."

Rob please post a link to the bypass solution. I am a VHF and up operator so I have a plethora of nice relays I can use. Collecting them is something of a a fetish. I also have some very well screened coax.

Scott was that a thinly veiled rebuke? I am a very busy man and do not have your fervour for all things on this forum, To me it is a tool not a way of life. Please refrain from such behaviour in the future.

I am sorry that I missed it but there is so much Scott omnipresence it has started to turn me and a few others off a little. As has the constant Anan evangelism.

I will not be asking for your help again until your learn to be gracious.